Pillow Block Buffer / Bench Mandrel

I want to Build a Pillow Block Buffer , in case your unfamiliar I included a (generic) picture, I had my pillow Block Custom Made with a 3/4 inch shaft that I can mount a 9 inch spindle sander drum on one end and a buffing wheel on the other .

I'm having a lot of trouble choosing a motor, jet and Baldor run 3/4 HP on their 3/4 inch shafts recommending 8 inch wheels , I'm going to run at least double that, probably 2HP


Now Brian House that manufactures the Revolution 2x72 grinders is a wealth of info,( And a really nice guy) https://housemade.us/pages/2x72-resources
But Im not sure I need as much as he is recommending ,
He really pushes a 3Ph motor with a VFD which gets you into a $650 just to power your machine,(actually closer to $700 once you wire everything) if I go that route I would actually be better off (financially) just to buy a Baldor or Jet. ( Save I dont get my custom Spindle sander Which would make mugs much easier)

so here is where im asking questions how much performance boost or electric bill savings will I get from the 3PH with the VFD versus an over HPed single phase farm duty motor ( I can get a 5HP single PH farm duty motor from the same manufacture for an additional $25 vs a 2HP 3PH),

I know variable speed is a great option, but is it worth$500, How Much does a VFD Bump your powerbill, the advantage of 3PH is it's more efficient, thus $ saving , does any of that transfer over when A VFD is used I would assume there is actually a power loss in a VFD and thus a cost


Thoughts?


thanks in advance
V/r HT1

P.S if you have your heart set on variable speed, it would be cheap and easy to do with a set of cone pulleys just like a drill press

 

A three phase motor is more efficient than a single phase motor, with three windings 120 degrees apart, they also are smoother torque than a single phase with two windings 180 degrees apart. VFDs are pretty efficient these days with it up around the mid 90's percent or higher. A VFD can be programmed with a soft start to go easy on your electrical system when starting.

So while the diagrams below aren't comparing apples to apples, you can see the single phase motors aren't getting above 70% efficiency while the three phase ones are over 90% when loaded. In Australia at least three phase motors are significantly cheaper than single phase.

Single phase motor efficiency:




Three phase motor efficiency:

 

This is really what I was asking.. my goodness how many years will it take me to pay off the cost of a Motor and VFD on a 10% savings, Ill do a little more research and try to get us a straight apples to apples comparison.


V/r HT1

 

Taking a step back here, the first post sounded like your goal is to have a buffer. Are you primarily interested in building and tinkering around with things, or do you just want a buffer and happen to have a pillow-block rigged up but are missing a motor?

Reason I ask is, all the back/forth about motors and phases sounds like perhaps you may be falling into the sunk-cost fallacy. Not being judgmental, if all you're after is to have a buffer, then just buy a purpose-built variable-speed buffer. It's illogical to base your choice on already having some parts on-hand (i.e. the "sunk-cost").

OTOH, if you're investment is emotional (you want to tinker with things), sunk-costs don't apply. In this case, do you really care about energy-efficiency and low-speeds? Isn't all/most buffing nearly always done at (very) high-speed?

If you really do need variable speed, perhaps consider simply having different buffing wheel sizes. No changing pullies or monkeying with electronics required. Swapping a 8" for a 6" wheel is (about) a 25% reduction in surface-speed (assuming I mathed correctly). Just an idea, take it or leave it, it's free

 

There are advantages to having a motor driven shaft versus a bench grinder: bench grinders are rare and expensive as the horsepower goes much above 3/4 Hp while any serious buffing needs much more than that. An edge case would be a robot polishing chrome truck bumpers with a 50 HP buffer spindle motor.

A motor driven spindle doesn't have the motor in the middle getting in the way of the job being processed as much as a bench grinder. Three phase motors and matching VFD's have come down a lot in price to the point where they are the same or cheaper than a single phase motor. Reliability is the same if not better: the thin "self healing" foil capacitors fail spectacularly and regularly in single phase motors but then the same can be said of VFD's.

As an example I found some Ebay three phase motors that were a good brand: ABB that were selling cheap. The motors cost (direct): AUD $30 for 1/2Hp, $40 for 1Hp and $50 for 2Hp so I bought eight of them and plan to make motorized spindles for diamond wheels, buffers and a dual tape belt grinder. These came from a motor company that was getting rid of excess stock. Here's some more of their deals: https://www.ebay.com.au/itm/3833466...MVWZTK&hash=item59413e2320:g:Wy0AAOSww~VeAVo6




So combine the $100 (inc delivery) 2Hp motor with a AUD $140 VFD and you get a 2Hp variable speed three phase motor with soft start for $240 versus a single phase 2Hp for AUD $249 delivered. A 2Hp bench grinder locally is AUD $1530 for comparison.

 

I have 4 buffers, and I have used many others, and what I really want is a very powerful buffer(Id love to Have the 5HP Baldor) without breaking the Bank, the 9 inch Spindle will allow me to make what is currently a tedious task, quick and simple.


I was very Shocked at the cost of a VFD, and really wanted to hear if it was worth my $$$ and I dont think it is (In my application) there is only two reasons to use a VFD
1: Need and dont have 3PH
2 Variable speed
Neither of which apply to me


Vr HT1

 

This is one of those situations (your point is well taken but the $'s are not common) i cant get a $100 2HP Motor I can get one pretty easy at $300(includes shipping) ,
the VFD if I go with the low end$140 VFD I will have it fail EXTREMELY quickly because of dust and water, I definitely need a higher end sealed VFD this one was recommended to me

https://www.amazon.com/KB-Electroni...fcdd39cd6581c&language=en_US&ref_=as_li_ss_tl

so im closer to $700... Still half the cost of a 2 HP Buffer

but for $90 i can install a set of cone pulleys for variable speed without any HP loss, put on up to a 5 HP single phase farm duty Motor(TEFC) for $300, so im saving $300 off the VFD 3PH option,
it seems Kelly has made it pretty clear that there is only about a 10% difference in electric use, so I'm not quite seeing why I shouldn't save the $300

So basically we said the same thing, but your situation is VERY best case scenario, I'm closer to middle of the road leaning a little farther out


V/r HT1


P.S. the Cone pully option also removes a prone to breaking electronic item (The VFD) so over the Buffers very long life i can expect a cost savings on repairs (alot of burnt out VFD stories out there in Knife making land)

 

maybe a few more pictures are needed to help explain what I have going on:

This is one of my most popular pieces a 57MM mug

they are made out of actual spent 57MM shells so they are very popular with the Navy and CG personnel the use the 57MM BOFORs Gun

to prepare the cast handles to be mounted (brazed) onto the shell I have to create a roughly 3inch Radius on the handle, and it needs to be straight up and down or the mug handle will not be straight up and down on the shell i rough this out with a rotary file and my delta spindle sander, which has 4.5 inch long sleeves so I have to do each end individually, stepping up to a 9 inch spindle sander is a $1500 option , and this is my only need for it so I wanted to build a custom pillow block buffer sander so I can do the handles quickly and easily



And yes I will have the other end available for a big buffing wheel (12inch) with power to spare

Now I'm really just working out how to power it . I had intended to use the power system from a 2X72 DIY belt grinder, but was shocked by the cost, particularly the VFD yes low ends ones are $150, but I have heard tons of stories of them falling and everyone (knifemakers) having to move up to the sealed $450 VFD's , I'll be throwing around brass dust , and I work outdoors so a cheap VFD is a NoGo


V/r HT1

 

Ahh okay, that wasn't clear to me, thanks for explaining your requirements better.

I was unaware that such powerful machines were even "a thing" A quick poke around ebay and a few tool sites confirms your assertion, wow! I've been told, for big industrial machines, the "best" source is industrial auctions. Of course then this requires "paying attention" time, and the transportation aspect is also a major hassle.

@HT1 It's infrequently suggested, but it is technically possible to have a "mobile" VFD. As in, use one VFD for multiple machines, either wire it to plugs or a rolling cart of some fashion.

I also had the thought to suggest maybe combining this with a 2x72 grinder, but you beat me to it Yes, they're expensive (along with their VFD) but also really really really useful in a metal shop. Here's someone adding a buffing-wheel to their homemade 2x72. I also agree that a cheap VFD is probably a bad idea. The recommendation I've read before is to size it 1.5x the HP rating of the motor you plan to use. Likely a 2x overrating wouldn't be too far-fetched either.

The high-quality units have over-current and over-voltage protection. The only thing they're typically missing is electrical surge protection (on the supply side). But large, in-line surge protectors have been "a thing" for quite some time now.

As long as the VFD is protected from heat/dust/environmental hazards, they're quite reliable. The only "wear" items in them are primarily heat sensitive, so as long as they're kept cool w/in their operating rangers, the unit will last a really long time. The high-quality sealed units have a giant heat-sink on the back, sometimes with a cooling fan (and alarm if the fan fails). So the only maintenance in your case would be keeping the heat-sink fins clean from dust and oil.

---

If you're into tinkering and more cost-sensitive, there is another option: A rotary phase converter.

These can be bought, but more importantly they can be made from (surprise!) a 3-phase motor and a bank of capacitors (for starting it on split-phase power). As Mark's castings suggested, the motors are relatively cheap, even giant 10+ HP units can be had on the used market for less than the cost of transporting them.

I haven't looked, but I'm sure there are plenty of tutorials online describing how to build a rotary converter. A friend of mine built two, for his lathe and milling machine. Other than the wiring everything up, they're conceptually quite simple, definitely cheaper than a VFD, but don't have any speed-control (which you said isn't necessary).

Even for someone untrained building one, the signs things aren't going well are fairly benign: The motor hums but doesn't spin, a (cheap/replicable) capacitor blows, or a breaker trips. Meaning, there's little risk to tinkering/learning how to get it working - assuming you have time and patients. If you don't have time and/or patients, then probably buying one or finding some local help is a better choice They can also be bought used.

 

For such a specialized unit: putting a radius on a mug handle, a single phase motor is the best option. Three phase and a VFD is better suited to lathes and drill presses where variable speed is a major improvement.

With motor frame sizes becoming a standard, we had often thought of casting some custom ends for an electric motor and extending the rotor shafts at both ends to make a powerful buffer/bench grinder.

 

https://www.automationdirect.com/ad...t_starters/ac_variable_frequency_drives_(vfd)
a 3Hp VFD new can be had for $200.
I have 2 VFD's in the shop one on my Mill and one on my Lathe. One is a AB 1HP and one is a 2 HP Automation direct. They both work well. As expected the AB (Allen Bradly) documentation is a bit easier to understand (but it starts @ double the price) You can find secondhand or new old stock 3PH motors for cheap. I've not done much polishing but if solid speed control is needed the VFD is the way to go. One of the other fun options on a VFD is that you can set it up to run faster than the rated RPMs. This can cause issues with motor bearings and doing it derates the output (just like running at very low speeds) but for some tasks it can be helpful to know that's an option.
You're a handy guy so $42 for a Nema rated steel enclosure (that's big enough to hold the VFD) should help keep it alive.

 

It sounded like HT1 is both cost and risk sensitive. That generally rules out low-priced imports, with the possible exception of spending lots of time waiting/searching the used market.

That's why I suggested building a rotary converter. The main cost of them is the (relatively cheap 3PH "idler" motor + time spent wiring everything up. They're not very energy efficient and require a bit more space, but I don't believe those were requirements. There're lots of plans/discussions online how to build them (example).

In my mind at least, finding a pair of used 3PH, fully-enclosed, fan-cooled motors should be pretty easy and cheap. The idler motor carries zero (physical) load, all it's there for is to spin its shaft and "fake" the 3rd phase. So only one of the motors needs to look pretty